1. Field of the Invention
This invention relates to a process for preparing copolymers. More particularly, this invention relates to a process for preparing a copoly(amide/peptide). Copolymers prepared in accordance with the process of this invention have many uses. For example, these copolymers can be used as biodegradable polymers and can be fabricated into useful shaped articles of manufacture, e.g., filaments, both mono-and multifilament, films, tapes, ribbons, rods, laminates, and the like.
2. Description of the Prior Art
Polymer compositions are disclosed in the prior art as having many and varied uses in industrial and commercial applications. For example, these polymers can be formed into filaments in which the polymer chains are oriented along the filament axis. Such filaments have many uses, in commercial applications, as for example, in the production of fibers for tire cord, textiles and the like. Similarly, these polymers can be fabricated into other useful shaped articles, as for example, films, gears, lawn mower housings, skate boards and the like, through use of conventional molding and fabrication techniques.
The utility of a particular polymer for a particular application is very much dependent on the physical properties of the polymer. For example, polymers having increased molecular weights form fibers and molded articles having superior properties. Fibers and molded articles made from such polymers have increased tensile strength, durability and impact resistance. Accordingly, processes for increasing the molecular weight of various polymers are valuable procedures in tailoring such polymers for optimization of such properties.
Similarly, various functional groups and polymer side chains, as well as the structural conformation of certain polymers, are factors which affect the physical characteristics of polymers and thus are also critical to the utility of these polymers. Thus, procedures for varying and controlling these function groups, side chains and structural conformations are also valuable tools in tailoring polymers for specific uses and as such are valuable tools to those of skill in the polymer art.
Certain conventional processes are used to form block, graft or quasi random copolymers of polyamides, or of polyamides and other polymer such as polyesters For example, U.S. Pat. No. 4,417,032 discloses a process for forming quasi-random copolymers from two or more homo polyamides. In this process, the homo polyamides are melt blended in the presence of a phosphite promoter Various copolyamides are also described in U.S. Pat. No. 2,892,817.
U.S. Pat. No. 3,509,107 discloses a process for increasing the relative viscosity of polyamide fibers or copolyamides by incorporating a phosphorous or phosphite compound into the polyamide under an inert gas atmosphere. The primary object of U.S. Pat. No. 3,509,107 is to provide a process for increasing the viscosity of polyamide fibers or copolyamides by incorporating a phosphorous or phosphite compound into the polyamide under an inert gas atmosphere. Another object of U.S. Pat. No. 3,509,107 is to provide a process for increasing the viscosity of polyamide yarn and cord which requires a minimum amount of gas. U.S. Pat. No. 3,551,548 (Brignac, et al., 1970) describes various optimizing procedures for U.S. Pat. No. 3,509,107. The described patents are each directed only to a method of producing polyamide yarn with increased viscosity via incorporating a phosphorous or phosphite compound into the yarn, and then heating said yarn in the presence of inert gas.
British Patent No. 569,184 discloses a method for producing a random copolymer from nylon 6 and nylon 6,6. The invention described herein teaches that heating a mixture of nylon 6 and nylon 6,6 results in interchange between various sections of the respective polymer molecules with the final product being a random copolymer of nylon 6 and nylon 6,6. In order to produce a random copolymer of nylon 6 and nylon 6,6, British Patent No. 569,184 teaches that it is necessary to heat the mixture of homopolymers for periods of time up to 8 hours at 285.degree. C. without any catalyst.
U.S. Pat. No. 4,390,667 discloses a process for decreasing the melt index and increasing the viscosity of polyamide fibers via incorporating a phosphate compound into the polyamide and heating the polyamide until the desired changes in the melt index and viscosity occur. The phosphate utilized in U.S. Pat. No. 4,390,667 includes substituted aryl phosphates which satisfy certain Hammett sigma values.
U.S. Pat. No. 4,417,031 discloses a process for preparing block and graft copolymers. The described process involves reacting two or more polyamides, polyesters, and homopolymers of .beta.-unsaturated carboxylic acids in order to form a graft and/or block copolymer. Included in the patent are copolymers formed from poly(caproamide) and poly(hexamethylene adipamide).
Diphenyl phosphoryl azide has been used as a convenient reagent for racemization-free peptide synthesis and for polymerization of peptides and amino acids such as .beta.-alanine and L-alanylglycine. See for example, Norio Nishi et al. "Polymerization of Amino acids or Peptides with Diphenyl Phosphoryl Azide (DPPA)", Int. J. Biol. Macromol., Vol. 2, p. 53 (1980) and Takayuki Shiori et al., "Diphenylphosphoryl Azide. A New Convenient Reagent for a Modified Curtius Reaction and for the Peptide Synthesis", J. of the American Chemical Society, Vol. 94, p. 6203-6205 (1972).